A wide variety of tin carboxylate compounds have been proposed for use as catalysts in the preparation of polyurethanes. Certain of these are in commercial use, either alone or as co-catalysts with tertiary amine catalysts. U.S. Pat. No. 3,164,557, proposes certain organotin compounds containing a tertiary nitrogen atom for use as polyurethane catalysts. The compounds in said patent correspond to the general formula ##STR1## wherein R.sub.1 and R.sub.2 are hydrocarbon radicals and X.sub.1 and X.sub.2 are stated to be organic radicals, at least one of which contains a tertiary nitrogen atom. Typical of the tin compounds thus proposed is ##STR2##
The use of organotin compounds containing tertiary nitrogen is also disclosed in British Pat. No. 899,948. The compounds therein disclosed are either unstable amino alkoxides containing a ##STR3## group (prepared from an alkanolamine and a tin oxide) or amino carbamates having a tin nitrogen bond. The tin nitrogen bond is much less stable than that in tin carboxylates.
Organo-substituted tin amino-carbamates, which are proposed for use as catalysts in preparation of polyurethane foams according to U.S. Pat. No. 3,796,674, also contain a tin nitrogen bond. The polyurethane foam catalysts disclosed in U.S. Pat. Nos. 3,681,271 and 3,703,484 are stannoxane type compounds, prepared by reacting a dialkyltin oxide with an acid or acid derivative. According to the earlier of these patents, the presence of a ##STR4## bond boosts the catalytic activity.